1. Field of the Invention
The present invention relates to a liquid crystal display device which carries out display of both the transmission display and the reflection display.
2. Description of the Related Art
A reflection/transmission type liquid crystal display device which carries out both the reflection display, which uses the external light, which is a light of the environment wherein the liquid crystal device is used, and the transmission display, which uses illumination light from the light source placed at a back side of the device.
A liquid crystal display device of this type, as disclosed in the Unexamined Japanese Patent Application KOKAI Publication No.H11-264964, has a liquid crystal layer arranged between the front side substrate, which is arranged at the observing side of the display, and the back side substrate, which faces the front side substrate, and at least one electrode which is provided on either one inner surface, of which the front side substrate and back side substrate oppose each other, and a plurality of electrodes to form a plurality of pixels on the other inner surface, which pixels are formed of regions wherein the plurality of electrodes and the at least one electrode face each other. A plurality of reflection films, each corresponding to pre-determined regions in the plural pixels, are provided behind the liquid crystal layer of the liquid crystal display device, and by the regions of pixels which the reflection films are provided, reflection parts are formed, wherein light enters from the front side and is reflected by the reflection films, and by the regions other than the reflection parts of the plural pixels, transmission parts are formed, which emit light to the front side by transmitting the light coming from the back side. Then, color filters to carry out color display, are provided in either one inner surface, of which the front side substrate and back side substrate surface, a front side polarization plate and a back side polarization plate are placed on the front and back side of a liquid crystal element respectively, and the light source is placed behind the back side polarization plate.
In an environment where the intensity of illumination is enough, this reflection/transmission type liquid crystal display carries out the reflection display using external light, and in a case where there isn't enough light, carries out the transmission display using the illumination light emitted from the light source. This reflection/transmission type liquid crystal display uses the reflection parts of the plural pixels of the liquid crystal element to carry out the reflection display, and uses the transmission parts of the plural pixels of the liquid crystal element to carry out the transmission display.
However, the conventional reflection/transmission type liquid crystal display device which displays color image, has a problem that the quality of the displayed image of the reflection display using external light, and the quality of the displayed image of the transmission display using light from the light source, are different from each other.
Namely, in the conventional reflection/transmission type liquid crystal display device which displays the color image, in a case of reflection display, light enters into the liquid crystal element from the front side of the liquid crystal element, and is reflected by the reflection film after transmitting the color filters and liquid crystal element, and goes out to the front side of the liquid crystal element after transmitting through the liquid crystal layer and color filters, and in a case of transmission display, light enters into the liquid crystal element from the back side, and through the liquid crystal layer and color filters, goes out to the front side of the liquid crystal element. Resulting to the outgoing light at the reflection display time being colored light, which transmitted to and from the liquid crystal layer and the color filters, and the outgoing light at the transmission display time being colored light, which transmitted through the liquid crystal layer and the color filter, just once.
Therefore, the emitted light in a case of reflection display has weaker optical power, compared to the emitted light in a case of transmission display. Therefore, the display quality of the liquid crystal display device, at the reflection display time, is not well.
Therefore, as disclosed in the Unexamined Japanese Patent Application KOKAI Publication No.H10-288706, colored parts and a white transparent parts formed in the pixel to brighten the reflection display, is proposed.
However, the liquid crystal element which has an aperture partially, in a part corresponding to the interior of the reflection part of the pixel of the color filter, is formed in a shape that the cross-section of the circumference of the aperture of the color filter is slanted diagonally to the normal line of the substrate. Therefore, it is difficult to accurately set the ratio of the colored light emitted from the region corresponding to the parts besides the aperture of the color filter, and the non-colored light emitted from the region corresponding to the aperture of the color filter, among the reflection part of each pixel, and the color reproducibility at the reflection display time becomes inferior.
Similar liquid crystal display device is disclosed in the Unexamined Japanese Patent Application KOKAI Publication No.H11-264964. The disclosure is incorporate herein by reference in their entirety.